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Disaggregated storage is a type of
data storage Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are cons ...
within computer data centers. It allows compute resources within a
computer server In computing, a server is a piece of computer hardware or software (computer program) that provides functionality for other programs or devices, called " clients". This architecture is called the client–server model. Servers can provide vario ...
to be separated from storage resources without modifying any physical connections. A form of
composable disaggregated infrastructure Composable disaggregated infrastructure (CDI), sometimes stylized as composable/disaggregated infrastructure, is an emerging technology that allows enterprise data center operators to achieve the cost and availability benefits of cloud computing us ...
, disaggregated storage allows resources to be connected via a
network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...
fabric providing flexibility when upgrading, replacing, or adding individual resources. It also allows servers to be built for future growth, offering greater storage efficiency, scale and performance than traditional data storage without compromising throughput and latency.


Background

In the past, data center storage existed in two forms. *
Direct-attached storage Direct-attached storage (DAS) is digital storage directly attached to the computer accessing it, as opposed to storage accessed over a computer network (i.e. network-attached storage). DAS consists of one or more storage units such as hard drive ...
– disks or drives attached to a single server.
Disk capacity Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a compute ...
and performance were available to that server, and only that server. Capacity expansion was limited to the number of
drive bays A drive bay is a standard-sized area for adding hardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed. Over the years since the introduction of the IBM PC, it and its compatibles have had many form ...
in the server or the limits of expansion chassis. Capacity and performance can scale-up (adding drives to a server) or out (by adding servers). *
Storage area networks A storage area network (SAN) or storage network is a computer network which provides access to consolidated, block-level data storage. SANs are primarily used to access data storage devices, such as disk arrays and tape libraries from ser ...
– disks or drives in a
storage array A disk array is a disk storage system which contains multiple disk drives. It is differentiated from a disk enclosure, in that an array has cache memory and advanced functionality, like RAID, deduplication, encryption and virtualization. Compone ...
which could be provisioned to one or many servers on the network. Capacity expansion is limited to the number of supported expansion chassis. Direct-attached storage has one critical advantage—it offers high-performance for any workloads running on that server. However, it comes with two critical disadvantages: Overall performance across the network is low, as storage can't be shared over the network without performance impact.
Capacity utilization Capacity utilization or capacity utilisation is the extent to which a firm or nation employs its installed productive capacity. It is the relationship between output that ''is'' produced with the installed equipment, and the potential output whic ...
is low because
disk capacity Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a compute ...
can't be directly used by other servers. Storage area networks are used to allocate storage to dozens or possibly hundreds of servers, which increases
capacity utilization Capacity utilization or capacity utilisation is the extent to which a firm or nation employs its installed productive capacity. It is the relationship between output that ''is'' produced with the installed equipment, and the potential output whic ...
, but storage area networks use specialized
network hardware Networking hardware, also known as network equipment or computer networking devices, are electronic devices which are required for communication and interaction between devices on a computer network. Specifically, they mediate data transmission in ...
and/or protocols that can come with disadvantages. Conventional storage networking does not provide sufficient throughput or latency minimization needed by many applications, and fails to provide enough bandwidth to utilize the full performance of new flash technologies.


Disaggregated storage overview

Disaggregated storage is a form of scale-out storage, built with some number of storage devices that function as a logical pool of storage that can be allocated to any server on the network over a very high performance network fabric. Disaggregated storage solves the limitations of storage area networks or direct-attached storage. Disaggregated storage is dynamically reconfigurable and optimally reconfigures physical resources to maximize performance and limit latency. Disaggregated storage provides the performance of local storage with the flexibility of storage area networks. A number of technology improvements are combining to make storage disaggregation a reality. These include: * Modern server performance: due to the PCIe Gen 4 serial bus, many servers can deliver more than 8 GB/sec of
throughput Network throughput (or just throughput, when in context) refers to the rate of message delivery over a communication channel, such as Ethernet or packet radio, in a communication network. The data that these messages contain may be delivered ov ...
, which far exceeds traditional storage networking performance capabilities. * The shift toward
NVMe NVM Express (NVMe) or Non-Volatile Memory Host Controller Interface Specification (NVMHCIS) is an open, logical-device interface specification for accessing a computer's non-volatile storage media usually attached via PCI Express (PCIe) bus. The ...
: The shift from disk to SAS/
SATA SATA (Serial AT Attachment) is a computer bus interface that connects host adapter, host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) ...
flash, and now NVMe flash, puts pressure on servers and networks alike. A single NVMe drive delivers millions of
IOPS Input/output operations per second (IOPS, pronounced ''eye-ops'') is an input/output performance measurement used to characterize computer storage devices like hard disk drives (HDD), solid state drives (SSD), and storage area networks (SAN). ...
, far beyond the usual capabilities of conventional storage networking. * 10Gb/ 25Gb/ 40Gb/ 100Gb
Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in ...
. More and more data centers are replacing slower network connections with faster Ethernet, removing
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
limitations and bottlenecks. Protocols like
NVMe-oF NVM Express (NVMe) or Non-Volatile Memory Host Controller Interface Specification (NVMHCIS) is an open, logical-device interface specification for accessing a computer's non-volatile storage media usually attached via PCI Express (PCIe) bus. The ...
on these very high bandwidth connections take full advantage of network improvements, removing bottlenecks, boosting performance and reducing latency. Different levels of storage disaggregation functionality exist, with the most flexible, full disaggregation, enabling storage capacity and/or performance to be provisioned from any storage device to any server on the network, then expanded, shrunk, or reprovisioned as new requirements emerge.


References

{{reflist Data processing